a) Field of the Invention
The present invention relates to a humidifier for producing moist or humid atmospheric air by supplying moisture to air in dry atmosphere.
b) Description of the Related Art
As a humidifier for producing a moist atmosphere, there are available a natural evaporation type humidifier, an electrically heating type humidifier, a water spray type humidifier, an ultrasonic type humidifier; however, they have peculiar problems. More specifically, the natural evaporation type humidifier is small in humidifying or moistening capacity, whereas the electrically heating type humidifier is high in running cost. Further, the water spray type humidifier tends to become large in size and is low in moistening efficiency, whereas the ultrasonic type humidifier suffers from problems in that it is short in service life and high in initial cost, and further it is liable to scatter bacteria and fine particles of calcium carbonate contained in the water.
Among these humidifiers described above, the natural evaporation type humidifier is still advantageous in that it is lower in running and initial costs and higher in safety as being less scattering bacteria and fine particles of calcium carbonate, except its moistening capacity is small. In view of the above-noted advantage, various attempt has been made to improve moistening capacity of the natural evaporation type humidifier, as disclosed, for instance, in Japanese Patents Laid-Open Nos. 171337/1985, 175421/1986, 237942/1986 and 50581/1994.
The humidifiers proposed in the Japanese Patent Publications are basically designed to increase the evaporation area while preventing air to be moistened from directly coming in contact with water. For example, the humidifier disclosed in Japanese Patent Publication No. 50581/1994 (corresponding to U.S. Pat. No. 5,318,731) employs the following arrangement: That is, as shown in FIG. 60, a tubular film member 248 is formed of a moisture permeable film which prohibits liquid water from permeate therethrough but permits water vapor to permeate or penetrate therethrough. Within the tubular film member 248, there is provided a spacer by which a water-containing space of several millimeters thick is secured. The tubular film member 248 with a corrugated spacer plate 249 placed thereon is wound up into a vortex configuration to define spaces into which air to be humidified is introduced. With this arrangement, it is possible to obtain a greater moistening capacity through the enlarged evaporation area in comparison to the conventional natural evaporation type humidifier wherein water is supplied to an open container, or a plate or cloth made of hydrophilic material, as well as to prevent scattering of bacteria and fine particles of calcium carbonate.
Even in the case of the humidifier of the natural evaporation type employing the tubular film member 248, there still exist some problems.
Problem 1: The spacer plate 249 is an important component for defining the spaces into which air to be humidified is introduced. However, the corrugated space plate 249 is structurally restricted in the crest-to-crest dimension with respect to the amplitude of the wave, and the ratio of the crest-to-crest length to the amplitude of the wave is not so high. Consequently, the space into which the air is introduced becomes unavoidably small, and resistance to the flow of the air becomes considerably high.
Problem 2: The space plate 249 is large in length, and the number of crests per projection plane is relatively large as the crest-to-crest length is not so great. Consequently, the total contact area between the tubular film member 248 and the crests is considerably large. Since the permeable-to-moisture function is impaired by the crest at portions where the tubular film member 248 and the crest contact each other, the moistening capability is lowered as much as the contact area is set larger.
Problem 3: Although winding the tubular film member 248 in the form of a vortex is effective to enlarge the evaporation area, that structure lengthens the time required to supply water therein. Further, since a very long tubular film member 248 ranging from 10 m to 40 m has to be dealt with, manufacturing is not so easy and thus the humidifier is low in productivity. In other words, the process of folding the long tubular film member 48 while putting the space plate 49 in between the folded sections renders the contents of work considerably complicated and thus makes automated production hardly possible.